The objective was to determine what importance the parameters controlling heat production may have in diagnostic thermography and prognostic evaluation of tumor growth capacity. In the anesthetized animal, tumor temperature was lowered and blood supply as well as O2 and glucose consumption were also lowered. As the temperature was raised in these tumors, a concomitant increase in blood supply and O2 and glucose consumption was obtained. However, warming of initially normothermic tumors failed to produce any consistent change in either blood supply or O2 and glucose consumption. Drastic alterations in circulation and blood oxygenation were necessary to appreciably (0.3 degrees C) modify tumor temperature and the results are neither consistent nor conspicuous.